Black_Rose2007/07/24 18:53:40조회수 87

2.00.05 - Lowboy

Low-frame semitrailers, lowboys, are mainly designed for transportation of highway or construction equipment, or any other super-heavy or large-dimension cargo.

The main characteristics of them are:

• maximum tonnage is – 20 – 150t (usually 35t for two-axle semitrailers)
• length – 14.1 – 14.6 m
• width – up to 3.18 m, with wideners
• inclination of the ladder – 9 – 18 degrees
• loading height (total height of the transported equipment and the semitrailer, in transport position, above the ground level) – up to 6 m.

The low loading height is essential to pass under bridges, power lines, in tunnels. The crearance of low-frame semitrailer is usually 230 mm. To reduce the loading height, lower-diameters wheels are used and also "double drop", when the load is positioned between the gooseneck and the rear cart of the trailer, below the cart level (length of the lowered area is usually 6.7 meters).

For more tonnage and safety, the lowboys are equipped with enforced leaf spring suspension, hydraulic pipeline, air brakes, and special stands at the front of the frame, to hold the semitrailer in horizontal position to facilitate the coupling with the tractor. Strength of the construction and quality of welding work is of special importance. The design allows for mechanical, hydraulic or electro-hydraulic means to lift the dovetail. The most advanced models of lowboys are also equipped with electric motors to adjust ground clearance by lifting the gooseneck.

The world leaders in low-frame semitrailer design are american design firms and engineering plants, holding the vast majority of patents in the field.